1. Technical Field
The subject matter disclosed herein relates to turbine systems. Specifically, the subject matter disclosed herein relates to turbine nozzles and/or vanes and turbine systems having such nozzles and/or vanes.
2. Related Art
Conventional combustion turbine systems typically include a compressor device for compressing inlet air and sending the compressed air to a combustor device, which mixes the compressed air with fuel. Once the compressed air is mixed with fuel, the air-fuel mixture is ignited to generate a hot gas flow, which can be provided to a turbine device to perform mechanical work. The turbine device generates power by passing the hot gas over a plurality of stator vanes and rotating blades of the turbine device. The stationary vanes and rotating blades can aid in power generation by directing the hot gas flow through the turbine device.
The efficiency of a conventional turbine system can be increased by increasing the temperature of the hot gas flow that passes through the turbine device. However, the ability to increase the temperature of the hot gas flow is limited by the ability of the stator vanes and the rotating blades to withstand the high temperature of the hot gas flow. More specifically, the fillet region (e.g., geometric transition zone between an airfoil and an endwall) of the vanes/blades is typically the first portion to suffer from mechanical failure when increasing the temperature of the hot gas flow within the turbine device. Conventionally, cooling features utilized by the vanes/blades. More specifically, conventional turbine vanes/blades include a plurality of cooling holes drilled directly into the fillet region or the airfoil portion of the vanes/blades. The cooling holes create a cooling passage between a cavity of an airfoil and the outside surface of the vane/blade. This passage provides cooling fluid (e.g., cooling air) throughout the vane/blade to reduce the temperature during operation of the conventional turbine system.
However, because the holes are drilled directly into the vane/blade at a shallow angle to the surface, spallation (e.g., fragmentation of a material layer) typically occurs during manufacturing. Spallation of a ceramic layer formed over the vane/blade can reduce mechanical strength, which may cause premature mechanical failure of the vane/blade. Spallation can also cause mechanical defects in the vane/blade, which can preclude the defective vane/blade from being used in a conventional turbine system.